Fixture for a grinding or polishing wheel

ABSTRACT

A fixture ( 1 ) for guidance of a tool having a cutting edge with respect to the periphery of a rotating grinding or polishing wheel ( 2 ), comprising a frame structure that runs along the periphery ( 6 ) of the wheel and has a guide formed as a slot ( 17 ) with an open other end, the slot providing a support surface ( 19 ) that is sloping relative to the radius of the wheel, and the inner end of the slot terminating radially within the periphery of the wheel on each side thereof, the fixture ( 1 ) in one end supported ( 11 ) for pivoting motion in a main plane of the wheel and in the other end carrying a separate balance weight ( 12 ).

TECHNICAL FIELD

The invention relates to a fixture for grinding/polishing of cuttingedges, in particular knife edges, by assistance from a rotatingpolishing- or grinding wheel. More specifically, the invention refers toa fixture for this purpose, being formed both to ensure a suitableworking pressure towards the wheel upon shaping the edge, and to securean optimal angle of operation. The fixture of the invention furtherprevents the treated subject to be positioned with the edge thereofplaced towards the rotational direction of the wheel, as well as theunintentional contact with the rotating polishing or grinding wheel.

BACKGROUND AND PRIOR ART

When sharpening edges, and when degrading or polishing raw edges,rotating grinding- or polishing wheels are often used. The edge is thenmanually positioned at a slanting angle to be treated by the rotatingperiphery of the wheel. When treating knife edges, e.g., the wheelrotates transversely to the knife blade from the back of the knifetowards the edge. When grinding/polishing the opposite side of the edge,the knife is swung round over it's ends. If the operator is untrained,there is a risk that the knife is instead turned about it's longitudinalaxis so the edge is directed towards the rotational direction of thewheel, in which case the knife may cut into the wheel and damage thegrinding- or polishing wheel. There is also a risk that the operator'sgrip on the knife is lost, and the knife being flung away by therotating wheel.

Another problem associated with a free manual handling of the knife isthat the grinding angle is difficult to control, and may also vary asthe knife is longitudinally moved across the periphery of the wheel thusproviding an unsatisfactory result.

Yet another problem is the risk of insufficient or excessive contactpressure applied to the wheel, in both cases resulting in unsatisfactorygrinding- or polishing operations.

The invention aims to provide an apparatus that eliminates above saidrisks and drawbacks associated with the manually controlledgrinding/polishing operation. This object is met in a fixture inaccordance with appended claim 1. Advantageous embodiments are definedin the subordinated claims.

SUMMARY OF THE INVENTION

Briefly, the invention foresees a fixture having a guide for a knifeblade, e.g., the guide being pivotally arranged on a grinding apparatusand based towards an operational position by means of a balance weightconnected to the fixture. The guide is formed to ensure an optimumoperation angle between the knife and the periphery of a wheel, and toprevent the knife blade from being wedged in the guide as a result offrictional engagement between knife and wheel. Furthermore, the contactpressure of the knife edge towards the rotating periphery of the wheelis limited through the pivoting attachment of the fixture, resulting ina dynamic adjustment of the knife blade and the fixture in relation tothe pressure applied from the balance weight.

SHORT DESCRIPTION OF DRAWINGS

The invention is more closely explained below with reference to theappended diagrammatic drawings, wherein

FIG. 1 is an embodiment shown in a partially sectioned view from oneside thereof;

FIG. 2 is a diagrammatic sectional view of the invention seen in thedirection of arrow II—II in FIG. 1, and

FIG. 3 is a view on larger scale showing a knife blade in position forgrinding/polishing in a sectioned view from the side.

DETAILED DESCRIPTION OF THE INVENTION

An example of a fixture 1 according to one embodiment of the inventionis diagrammatically shown in FIGS. 1-3, the following disclosure beingdirected towards an implementation for treatment of knife edges. Itshould however be pointed out that the shown example does not excludeembodiments adapted for cutting edges of different kinds, such as axes,chisels, plane irons, scissors, hedge shears, pruning shears, and othertools having cutting edges suitable for being sharpened.

A grinding or polishing apparatus has a wheel 2 rotatably carried on ashaft 3 inside a protective housing 4, and rotated in direction of arrowR by means of a motor (not shown). A window 5 in the protective cover 4provides access to a portion of the wheel 2, through which window theknife edge is applied in contact with the periphery 6 of the wheel.

The fixture 1 is attached to the cover 4 or to equivalent structures ofthe grinding/polishing apparatus by suitable attachment means. To thispurpose, the shown embodiment foresees an attachment means 7 having twolegs reaching on opposite sides of the cover 4 in the shape of a clamp.The clamp 7 is connected to the cover 4 by means of a bolt 8, reachingthrough a pair of slots 9 formed in each leg, respectively, of theclamp. Through this attachment, the clamp 7 may be pivoted about thebolt 8 in any desired angular position in relation to the window 5 ofthe cover, and may also be displaced axially on the bolt 8 for adjustingthe circumferential position of the fixture relative to the periphery 6of the wheel.

A frame structure 10 included in the fixture is carried in the free,upper end of the clamp 7. The frame 10 is pivotally connected with theclamp 7 by means of a shaft 11, forming a pivot to the frame forpivoting motion in a main plane of the grinding/polishing wheel. Thepivot axis 11 of the frame is adjustable with respect to the periphery 6of the wheel, and also with respect to it's circumferential positionoutside the periphery 6 through the adjustable attachment of the clamp 7as previously explained.

A balance weight 12 is arranged in the opposite end of the frame 10. Theweight 12 is preferably supported for axial adjustment on a bar 13,fixedly accommodated in the end of the frame 10. To this purpose, theweight 12 may be internally formed for threaded engagement with a thread14 that is formed externally on the bar. The contact pressure appliedfrom the fixture and knife edge towards the periphery 6 of the wheel maythus be controlled, and an accurate operation pressure secured, throughthe balance weight 12.

The frame 10 preferably has a generally U-shaped section, with twoopposing side members connected through a back member such that theframe embraces the wheel 2 like a saddle over the opening 5 of the cover(see also FIG. 2). In a resting position, the fixture 1 rests againstthe cover 4 or other structural element of the grinding apparatus, forexample as is illustrated at 15 and 16, respectively, in FIG. 1 of thedrawings.

A slot 17 having an open upper end extends sloping from the back memberof the frame 10, down through the side members and for a distancesufficiently long to terminate the slot radially inside the periphery 6in an operative position of the fixture (see FIG. 3 specifically). Thesloping angle of the slot relative to the radius of the wheel, as seenthrough the contact point of the knife edge with the wheel periphery,may be adjusted and optimized through the adjustable attachment of theclamp 7 as previously discussed. The slot 17 has a width that permitsinsertion of a knife blade 18, whereby the slot lower surface defines agenerally U-shaped support 19 for the lower side of the knife blade. Theinner end of the slot 17 comprises a pair of insert limitations 20arranged on both side members, said limitations being spaced from thesupport surface 19 by an intermediate distance that is generally adaptedto the thickness of the knife blade.

The insert limitations 20 are at least partially arc-shaped and thusproviding a pointed contact P with the knife blade a8 inserted in theslot 17. Preferably, the insert limitations 20 are circular discs androtatably supported (see arrow r in FIG. 3) on the side members of theframe by means of bolts 21. Alternatively, the insert limitations may beoval in shape and pivoted to a position, fixed by the bolts 21, in orderto adjust the distance from the support surface 19. Another alternativeforesees that the insert limitations are biased towards the supportsurface 19. Preferably, the insert limitations 20 are produced from amaterial that is softer than the edge, such as synthetic material likeplastic or Nylon®, in order not to damage the knife edge as the knife isinserted in the slot 17.

When grinding/polishing, the knife blade is inserted in the slot 17 withthe side of the blade contacting the support surface 19 far enough forthe knife edge 22 to bear against the periphery 6 of the wheel,whereupon the knife is longitudinally slided through the slot fortreatment of substantially the total length of the knife edge. Theinsert limitations 20 are adjusted for limitation of the insert depth ofthe knife blade in the slot, through a point shaped contact with theknife behind the knife edge at an area where the thickness of the bladeis decreasing and successively merging with the edge. The concentratedcontact point permits the knife blade to be longitudinally moved throughthe slot, against a limited and reduced frictional resistance.

With the fixture 1, grinding or polishing may be performed under acontact pressure determined by the weight and/or adjusted position ofthe balance weight, and under an optimized treatment angle. The knifeblade is inserted in the slot 17 for a distance determined by the insertlimitations 20, whereupon the knife is forced by the rotating peripheryof the wheel to be pressed against the insert limitations. Therotational movement of the wheel urges the knife towards the inner endof the slot, while concurrently pressing the knife towards the insertlimitations and Lifting the fixture against the weight of the balance12. The fixture is thus pivoted about the axis 11 of clamp 7 and loadingit's weight upon the knife edge. The insert depth of the knife in theslot is therefore not critical for the work result, since the fixture isdynamically adjusted through the pivoted movement in order to exert asubstantially uniform pressure to the knife edge as the knife islongitudinally moved through the slot. Thus, the sliding movement may beperformed without specific care for a manually controlled pressure,since the operative pressure is controlled by the fixture thatdynamically adjusts the load placed on the knife edge via the insertlimitations 20.

The fixture disclosed above may be modified in respect of detailedstructures and design without departing from the general solution asdefined in appended claims. A central aspect of the invention is thatthe fixture is pivotally supported in the main plane of the grindingwheel for a dynamic adjustment and adaptation to the oppositely directedpressure exerted from the wheel, against the load of an adjustablebalance weight that determines the operative pressure. Additionaladvantages include an optimized and adjustable angle for the treatedknife edge, and for the preferred embodiment, also an enclosure thatprevents damages from the accessible operative portion of the wheel.

An alternative embodiment foresees a fixture having a guide for acutting edge to be grinded/polished, the fixture extending on one sideonly of the grinding wheel. Preferably, the single side fixture isattached to the side turning towards the operator and thereby preventingunintentional contact with the rotating wheel. This embodiment mayotherwise be designed in correspondence with the fixture shown in FIG.1, except for the guiding slot instead having a supporting surface ofelongate shape, or with an angled outer end. This less complex fixturemay be pivoted about an axis 11 and carried by an arm 7, the armattached to the grinding apparatus substantially as described above.Furthermore, the insert limitation may be shaped otherwise and realizedas an arm, e.g., with an arcuate portion, or as a half-moon shapedelement attached to the external side of the fixture. These and othermodifications appreciable by the man skilled in the art are all includedin the conceptual solution as defined by the appended claim.

1. A fixture (1) for guidance of a tool having a cutting edge withrespect to the periphery of a rotating grinding- or polishing wheel (2),characterized in that the fixture in it's operational position extendsmainly along a portion of the periphery (6) of the wheel and has a guideformed as a slot (17) opening away from the periphery of the wheel, theslot providing a support surface (19) for the tool, said support surface(19) being arranged at a sloping angle relative to a radius of the wheelgoing through the point of contact between the tool edge and theperiphery of the wheel, and the inner end of the slot terminatingradially within the periphery (6) of the wheel at least on one sidethereof, the fixture (1) in one end supported (11) for pivoting motionin a main plane of the wheel and in the other end carrying a separatebalance weight by which the fixture is biased towards the periphery (6)of the grinding- or polishing wheel.
 2. The fixture of claim 1,characterized in that the weight (12) is adjustable with respect to adistance from the pivot point (11) for adjusting the load of the fixtureand thus the contact pressure from the edge bearing on the periphery ofthe wheel, in operational position.
 3. The fixture of claim 1,characterized in that the slope angle of the slot (17) relative to theradius of the wheel going through the point of contact between the tooledge and the periphery of the wheel is controllable through adjustmentof the pivot point (11) with respect to a radial distance from thecentre of the wheel (2).
 4. The fixture of claim 1, characterized inthat the slope angle of the slot (17) relative to the radius of thewheel going through the point of contact between the tool edge and theperiphery of the wheel is controllable through adjustment of the pivotpoint (11) with respect to it's circumferential position outside theperiphery (6) of the wheel.
 5. The fixture of claim 1, characterized byan insert limitation (20) opposite the support surface (19), thelimitation having an arcuate surface for pointed contact (P) with a toolthat is inserted in the slot (17) to rest against the support surface(19).
 6. The fixture of claim 5, characterized in that the limitation(20) comprises a pair of discs, one disc being arranged on each side ofthe fixture, respectively.
 7. The fixture of claim 6, characterized inthat the limitation (20) is rotatably supported and manufactured from amaterial that is softer than the edge to be treated, such as a syntheticmaterial and preferably plastic or Nylons®.
 8. The fixture of claim 6,characterized in that the disc is biased towards the support surface. 9.The fixture of claim 6, characterized in that the disc is oval in shapeand may be fixedly secured in the subject angular position.
 10. Thefixture according to claim 1, characterized in that two side membersconnect to a back member that embraces opposite sides of an accessibleportion of the wheel periphery substantially like a saddle, and thesupport surface (19) is U-shaped in a planar view.
 11. The fixtureaccording to claim 2, characterized in that two side members connect toa back member that embraces opposite sides of an accessible portion ofthe wheel periphery substantially like a saddle, and the support surface(19) is U-shaped in a planar view.
 12. The fixture according to claim 2,characterized in that two side members connect to a back member thatembraces opposite sides of an accessible portion of the wheel peripherysubstantially like a saddle, and the support surface (19) is U-shaped ina planar view.
 13. The fixture according to claim 3, characterized inthat two side members connect to a back member that embraces oppositesides of an accessible portion of the wheel periphery substantially likea saddle, and the support surface (19) is U-shaped in a planar view. 14.The fixture according to claim 5, characterized in that two side membersconnect to a back member that embraces opposite sides of an accessibleportion of the wheel periphery substantially like a saddle, and thesupport surface (19) is U-shaped in a planar view.
 15. The fixtureaccording to claim 6, characterized in that two side members connect toa back member that embraces opposite sides of an accessible portion ofthe wheel periphery substantially like a saddle, and the support surface(19) is U-shaped in a planar view.